you mustn't throw wastes everywhere in the park when you have a picnic there.(改为同义句）
问题描述：
you mustn't throw wastes everywhere in the park when you have a picnic there.(改为同义句）
答
you are not allowed (或forbidden) to throw wastes everywhere in the park when having a picnic there 因为主句和从句主语一样,所以从句的主谓可以省略,再把动词变为动名词